1. Field of the Invention
The present invention relates to an image processing method and apparatus, which can :perform a color print operation of characters, figures, raster images, and the like on the basis of print data, commands, and the like supplied from a host computer.
2. Related Background Art
FIG. 1 shows an example of a coordinate system (to be referred to as a user coordinate system hereinafter) serving as a reference for coordinate points to be designated when figures, characters, and the like are drawn using a PDL (Page Description Language) or page description commands.
A hatched rectangular portion indicates an effective print area (a drawing enable area in a sheet). As shown in FIG. 1, the length of the effective print area will be referred to as an effective print area height hereinafter, and the width of the effective print area will be referred to as an effective print area width hereinafter.
The coordinate system shown in FIG. 1 is a two-dimensional x-y orthogonal coordinate system, and has an origin located at the lower left corner of the effective print area, as shown in FIG. 1.
Any coordinate unit (e.g., 0.01 mm or 1/72 inch) can be arbitrarily set in this coordinate system.
Description elements of the PDL and page description commands for, e.g., figure drawing, which are set on the basis of the above-mentioned user coordinate system, are analyzed in an image processing apparatus in the order they are received, and are converted into information to be developed into a memory.
FIG. 2 shows an example of a coordinate system (to be referred to as a printer coordinate system hereinafter) serving as a reference when the above-mentioned memory development information is generated.
The coordinate unit of this coordinate system is determined by the resolution of the image processing apparatus (for example, when the resolution is 300 dpi, the coordinate unit is 1/300 inch).
A hatched rectangular portion is the same as the effective print area shown in FIG. 1.
This coordinate system is a two-dimensional x-y orthogonal coordinate system, and has an origin located at the upper left corner of the effective print area.
FIG. 3 shows an example of a memory map of an internal RAM area in a conventional image processing apparatus for performing a color print operation on the basis of the PDL or page description commands.
The RAM area is constituted by a system work memory, a reserved area, and page development memories (each having a size corresponding to the effective print area shown in FIG. 2) for Y (yellow), M (magenta), C (cyan), and Bk (black) as coloring agents ( toners or inks ).
The system work memory is used as a storage area of information (e.g., variables) used to control the image processing apparatus, and a permanent work area.
The reserved area is used as an area for storing memory development information, a character cache memory, and the like.
FIG. 4 shows an example of a line color designation command of drawing attribute designation commands.
This command is used for designating a color of a line or an outline of a figure.
A command number varies depending on the drawing attribute designation commands, and is used for identifying each command function.
The content of a number-of-data parameter indicates the number of data input after the number-of-data parameter.
In this case, the content of the number-of-data parameter of the line color designation command is 4.
Y-, M-, C- and Bk-values respectively indicate density data values of Y (yellow), M (magenta), C (cyan), and Bk (black) as primary colors of coloring agents.
FIG. 5 shows an example of a circle drawing command of drawing commands.
A command number varies depending on the drawing attribute designation commands, and is used for identifying each command function.
The content of a number-of-data parameter indicates the number of data input after the number-of-data parameter.
In this case, the content of the number-of-data parameter of the circle drawing command is 3.
The x- and y-coordinates of the center are those on the user coordinate system.
An actual radius is calculated by multiplying a coordinate unit of the user coordinate system with a "radius" value.
FIG. 6 shows an example of memory development information generated by analyzing the line color designation command shown in FIG. 4.
A command table number is used for identifying each memory development information. Other parameters are the same as those in FIG. 4.
FIG. 7 shows an example of memory development information generated by analyzing the circle drawing command shown in FIG. 5.
A command table number is used for identifying each memory development information. Values xc and yc represent the coordinates of the center of a circle on the printer coordinate system.
A value r represents a radius value converted to have the resolution of the image processing apparatus as a unit.
FIG. 8 shows a case wherein on the user coordinate system shown in FIG. 1, the coordinate unit is set to be 1 mm, and drawing of a circle having coordinates (150, 150) for the center and a radius of 50 is set.
FIG. 9 shows an example of a command issued when the circle drawing operation shown in FIG. 8 is set.
FIG. 10 shows a case wherein the circle drawing operation on the user coordinate system shown in FIG. 8 is converted into a circle drawing operation on the printer coordinate system having a coordinate unit =1/300 inch (about 1/11.8 mm).
As shown in FIG. 10, the effective print area height is set to be 400 mm.
The x-coordinate of the center is 1,770 (150.times.11.8), the y-coordinate is 2,950 (250.times.11.8), and the radius is 590 (50.times.11.8).
FIG. 11 shows an example of memory development information of the circle drawing operation shown in FIG. 10, which information is generated by analyzing the circle drawing command shown in FIG. 9.
FIG. 12 shows an example of a line color designation command issued when the circle drawing operation shown in FIG. 8 is performed using yellow (a color corresponding to the coloring agent at a density of 100%).
Note that each of the Y-, M-, C-, and Bk-values falls within a range of 0 to 255. In this case, the Y-value is 255, and other values are 0.
As described above, to control a conventional image processing apparatus for performing a color print operation on the basis of the PDL or page description commands, development memories each having a size corresponding to the effective print area of a sheet are used for Y (yellow), M (magenta), C (cyan), and Bk (black) as coloring agents of toners or inks.
However, the conventional apparatus suffers from the following drawbacks.
(1) When color print control is performed based on the PDL or page description commands in, e.g., an ink-jet printer which can interrupt recording at a halfway position of a sheet, and can restart recording, Y, M, C, and Bk memories each having a size corresponding to the effective print area of a sheet are not always required, so the memory cannot be efficiently utilized. PA1 (2) Since recording is started after all the page description elements or page description commands for recording one page are analyzed, and figures, characters, or the like are developed into a memory, it takes much time for drawing. PA1 (3) When color print control is performed based on the PDL or page description commands in, e.g., an ink-jet printer which can move a print head in the vertical and horizontal directions, control is not made to move the head within only a drawing range, or to print only the content of a memory which actually stores a drawing pattern of the Y, M, C, and Bk memories in the drawing range, resulting in the long drawing time.